An insulation film having a lower relative permittivity is required, as electronic devices, multilayer wiring boards, etc. are increasingly small-sized and highly integrated, and as displays of e.g. TFT are large-sized and become high-resolution. Further, as an optical material to be used for an optical transmission device such as an optical integrated circuit, an optical switching device or an optical-electrical consolidated substrate, a material having high light transmittance and low birefringence (dependency on polarization of refractive index), is required. Fluorinated aromatic polymers are now being studied to satisfy such requirements and to secure heat resistance of at least 250° C., preferably at least 300° C., which is required in the process for producing and/or mounting electronic devices, multilayer wiring boards or optical transmission devices.
As a fluorinated aromatic polymer, a fluorinated aromatic polymer having ether bonds (hereinafter referred to as a polyarylene ether or PAE) has been proposed (e.g. Patent Documents 1 to 3 and Non-Patent Document 1). Its relative permittivity is from about 2.5 to 2.9, and its application to an insulation film for electronic devices or multilayer wiring boards, is being studied. Further, its application to optical transmission devices is also being studied.
Further, PAE having a branched structure has been proposed which is produced by using a compound having at least three phenolic hydroxyl groups (e.g. Patent Document 4).
Further, PAE satisfying both low dielectric constant and high glass transition temperature (hereinafter referred to as Tg) has been proposed which is produced from a specific fluorinated aromatic compound having a branched structure (e.g. Patent Documents 5 and 6).
Further, a transmissive liquid crystal display device having an interlayer insulation film comprising a highly transparent fluorinated organic thin film has been proposed (e.g. Patent Document 7). Such an organic thin film is required to have high transparency, a low dielectric constant and high surface flatness so as to increase the aperture ratio.
Patent Document 1: Japanese Patent No. 3064011
Patent Document 2: U.S. Pat. No. 5,115,082
Patent Document 3: U.S. Pat. No. 5,959,157
Patent Document 4: JP-A-10-247646
Patent Document 5: WO03/008483
Patent Document 6: JP-A-2005-105115
Patent Document 7: JP-A-9-90404
Non-Patent Document 1: J. Polm. Sci.; Part A; Polm. Chem., vol. 36, 2881 (1998)